there should be an O ring at the top to seal the dipstick in the tube. At least I have one on mine

Ian.....tube not dipstick loose.

Ard. When my engine dipstick tube was loose (just a push fit) I tried opening out tube but to no avail as I just could not get dia. just right to be a good push fit. In the end I thoroughly cleaned inside the hole, around the engine surface surrounding and the tube and glued it back in. I either used Araldite or JB Weld. One of the many Loctite products may be used instead of glue. There is a small shoulder in the engine hole that the tube sits against so the correct length of tube protrudes from the engine and the dipstick protrudes the correct amount into the engine to give correct oil level. I don't know if gearbox has similar set up.
Stick at it

Hi guys, just had the result of someone aralditing in a dipstick tube. Boy did we have fun removing it so that the engine block would fit past the tool post on the facing machine. When I put it back, I used aero grade loctite. Best to think ahead if the engine ever needs rebuilding

Therefore, I only lightly dusted it and got the block warm - then managed to wiggle the tube free with mole grips over a taped up area so I then put it back with a thread sealant that I know gives way at a low torque as by this time it had worn quite loose.